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Objectives To evaluate the clinical characteristics, disease burden, and treatment patterns of peripheral spondyloarthritis (pSpA) patients with and without psoriasis using data from the ASAS-perSpA study. Methods We included 433 patients who had a diagnosis of pSpA according to the rheumatologist’s diagnosis from the ASAS-PerSpA study. The presence of a personal history of psoriasis was defined as the presence of signs of psoriasis at physical examination or the presence of psoriatic nail dystrophy, including onycholysis, pitting and hyperkeratosis, or a history of psoriasis diagnosed by a physician. Clinical characteristics, patient-reported outcomes and treatment pattern were compared between subgroups with and without psoriasis. Results A total of 83 patients (19.2%) had a personal history of psoriasis. Patients with psoriasis were older (48.4 vs 43.2 years) and had a longer diagnostic delay (7.4 vs 3.5 years), a higher frequency of dactylitis (36.1 vs 20.0%) and enthesitis (65.1 vs 55.4%) than patients without psoriasis. A longer diagnostic delay (odds ratio [OR] = 1.06 [95% CI 1.01, 1.11]), lower odds for HLA-B27 positivity (OR = 0.31 [95% CI 0.15, 0.65]) and higher odds for enthesitis (OR = 2.39 [95% CI 1.16, 4.93]) were associated with the presence of psoriasis in a multivariable regression analysis. While patient-reported outcomes were comparable between groups, a higher use of biologic DMARDs was observed in patients with vs without psoriasis. Conclusion The presence of psoriasis has an impact on clinical characteristics of pSpA. pSpA patients without psoriasis were less frequently treated with biologic DMARDs despite similar disease burden as compared with patients with psoriasis.

Objective To evaluate the diagnostic value of SpA parameters and their combination for the diagnosis of axial SpA in patients with an a priori different probability of the diagnosis. Methods A total of 361 patients with chronic back pain and suspicion of axial SpA (181 referred by primary care physicians or orthopaedists, 180 recruited via an online screening tool) received a structured rheumatologic examination, which resulted into a diagnosis or exclusion of axial SpA. The prevalence of axial SpA indicating the pre-test probability was 40% in the physician-referred subgroup and 20% in the online screening subgroup. Sensitivities, specificities and likelihood ratios for SpA features were determined in both subgroups and the respective post-test probabilities of axial SpA were calculated. Results The relative diagnostic value of single SpA features varied substantially between the groups with different referral pathways. For instance, HLA-B27 positivity increased the probability of the presence of axial SpA by 35% to 55% in online-screened patients and by 22% to 62% in physician-referred patients. The absence of HLA-B27 resulted in a sharp decrease in the probability of the presence of axial SpA in physician-referred patients (from 40% to 6%). This decrease was less sharp in the online screening group (from 20% to 10%). These differences were especially relevant in patients with a small number (one to two) of positive SpA features. Conclusion The diagnostic value of SpA features varies in different patient populations, which should be considered in the diagnostic approach.